The present invention relates to vehicles. More specifically, the present invention relates to battery monitors used to monitor batteries used in vehicles. Vehicles, both automotive and electric, typically include a storage battery. For example, automotive vehicles powered by combustion engines typically include a battery. The battery is used to power the electrical system when the engine is not running. Additionally, the engine is used to charge the battery. The engine is also used to power electrical components of the vehicle when the engine is running.
It has typically been difficult to monitor the condition of the storage battery used in such vehicles. This difficulty relates to all of the variables which are factors in determining the condition of the battery, as well as the electrical connections which are made to the battery during its use. Attempts have been made to characterize the operation of a battery and use xe2x80x9ccharacterization curvesxe2x80x9d to determine battery condition. However, this technique is often quite difficult to implement because it is difficult to determine which particular characterization curve the battery may be following as well as precisely where on a particular characterization curve a battery may lie at a given moment.
This has made it difficult for a vehicle operator to accurately and in real time determine the condition of the vehicle""s battery. For example, a battery at a particular moment may have just sufficient output to start the engine of a vehicle but provide no outward indication to the operator that the vehicle will not be capable of starting a second time. Further, a battery that is capable of providing sufficient power at one temperature, may fail the next morning if the temperature drops over night.
Some attempts have been made to monitor the condition of a battery using xe2x80x9ccoulomb countingxe2x80x9d in which the amount of charge accepted by the battery or removed from the battery is monitored. However, such techniques have required a starting point (i.e., an initial value) in order to begin any attempt to monitor battery condition. Further, such techniques may not account for situations in which the battery is fully charged and any additional current going into the battery is simply lost as heat or a situation in which the battery charge decreases during periods on non-use. Thus, it would be desirable to have a battery monitor which is capable of monitoring the condition of a battery in a vehicle.
In one aspect, an apparatus and a method of monitoring a battery in an automotive vehicle are provided. A stored battery parameter value is set to an initial value, measuring a first parameter of the battery during a period when an engine of the vehicle is not operating. The stored battery parameter value is changed as a function of the measured first parameter. A second parameter of the battery is measured during a period when the engine is operating. The stored battery parameter value changed as a further function of the measured second parameter. An output related to a condition of the battery is provided as a function of the stored battery parameter value.
In another example aspect, a battery parameter minimum threshold value is retrieved from a memory and a measured battery parameter value is obtained. A maximum threshold battery parameter value is also retrieved. A battery condition is determined as a ratio of two quantities and as a function of the battery parameter minimum threshold value, the measured battery parameter value and the maximum threshold battery parameter value.